Methods and apparatus for manufacturing helical products

ABSTRACT

Methods and apparatus for forming devices including dead-ends and insulator ties from flat and other strips of material, as well as the devices themselves, are disclosed. Components of these devices may be formed continuously from a single strip, avoiding the need to weld or clamp the components together. Forming the devices in this manner reduces the possibility of stresses or non-uniformities forming when the components are joined and permits continuous automatic or semi-automatic manufacture to occur.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 08/334,136 (now U.S. Pat. No. 5,586,461), filed Nov. 4, 1994.

This invention relates to methods and apparatus for manufacturinghelical products (including but not limited to insulator ties anddead-ends) and to such products themselves.

Conventional helical products such as dead-ends and insulator tiestypically consist of sets of wire strands. After the individual strandsare formed, they are spiralled and then glued together to form thestranded sets. In many cases grit is then sprayed onto the glued sets toraise their collective coefficient of friction, and portions of each setare thereafter straightened as appropriate to produce the resultingproduct. This straightening technique can cause the glued strands todetach, however, and the overall formings process is often laborintensive.

U.S. Pat. No. 3,847,491 ("the '491 patent") to Poffenberger disclosesother helically preformed dead-ends and "splice-type" appliances forcable and wire installations. According to the '491 patent, thedead-ends may be constructed of either plastic rods or a flat ribbon orstrip of material such as steel. Following separate formation of the twohelical legs and a U-shaped bight of each dead-end, the three elementsare joined by welding or clamping them together. The dead-ends may alsocontain knurled or gritted surfaces to enhance their ability to gripcables, although no mechanism for knurling the appropriate surfaces isdisclosed in either the '491 patent or in U.S. Pat. No. 3,183,658 towhich it refers.

U.S. Pat. No. 3,800,397 ("the '397 patent"), also to Poffenberger,addresses a method for making the helical legs and bight of thedead-end. As stated therein, each leg is created by forming an elongatedhelical strip and then cutting the strip to the desired length. Anothercontinuous strip is formed into "continuous generally sine wave typeundulations," with "each individual undulation corresponding to thedesired configuration" of the bight of the resulting dead-end. Theundulating strip is cut to define multiple bights, one of which may thenbe joined to the helical legs as noted above to create the dead-end.

As discussed in the '491 and '397 patents. the pitch lengths of the twohelical legs differ. In use, the first leg (having longer pitch) iswrapped about a cable, with the second leg thereafter wrapped about boththe cable and the first leg. The helixes of the first leg purportedlyprovide a body of a relatively uniform and more rigid contour for thehelixes of the second leg to grip, while the second leg is intended toclamp the surface of the first leg tightly about the cable.

Neither the '491 patent nor the '397 patent contemplates manufacturingboth the helical and bight portions of dead-ends from a continuous stripof material. Similarly, neither patent discloses forming otherappliances usefull in connection with cable installations or anymechanism for knurling such appliances in-line. The '491 and '397patents additionally neither teach nor suggest devices having legs ofequal pitch length, each intended to wrap around a conductor or othercable. Instead, as discussed therein, the leg of the dead-end of the'491 and '397 patents having the shorter pitch is wrapped around theother leg to diminish excessive localized radial pressures thatotherwise purportedly would occur.

FR-A-706920 discloses apparatus in which strip material is urged topress against selected pairs of rollers disposed at an angle to thedirection of travel of the strip material. One of the rollers carries ashoulder against which an edge of the strip material bears. The stripmaterial is deformed by contact with the rollers into the form of ahelix.

The present invention provides a method for forming helical sections instrip material, the method comprising the steps of:

a) feeding the strip material in a first direction to contact a pair offorming members;

b) the forming members acting to bend and twist the strip to form ahelical section leaving the forming members in a second direction, thedegree of bending determining the diameter of the helix and the degreeof twisting determining the helical angle of the helix characterised inthat

c) the strip material passes from one side of the pair of formingmembers, between the pair of forming members, to exit from the otherside of the pair of forming members.

The present invention further provides apparatus for performing theabove mentioned method comprising

a) means for feeding strip material in a first direction to contact

b) a pair of forming members operable to bend and twist the strip toform a helical section leaving the forming members in a seconddirection, the angle between the first and second directions determiningthe helical angle of the helical section characterised in that

c) the forming members are disposed such that the strip material passesfrom one side of the pair of forming members, between the pair offorming members, to exit from the other side of the pair of formingmembers.

Optionally the forming members may comprise spaced rollers withrotational axes angularly disposed to the first direction to lieparallel with the second direction.

The present invention further provides a method of producing helicaldevices comprising a first helical section, a second non-helicalsection, and a third helical section, characterised in that the methodcomprises the steps of:

feeding strip material having integrally formed first second and thirdsections to an apparatus;

b) within the apparatus automatically activating helix forming means toform the first section into the shape of a helix;

c) within the apparatus automatically inactivating the helix formingmeans so as not to form the second section into the shape of a helix,

d) within the apparatus automatically activating the helix forming meansso as to form the third section into the shape of a helix

e) cutting the first section, second section, and third section from thestrip material to form a first helical device; and

f) repeating steps a)-e) to form a second helical device.

This invention thereby provides alternative methods and apparatus forforming helical devices of many types (including dead-ends and insulatorties). Unlike the devices of the '491 and '397 patents, the componentsof the devices of the present invention may be formed continuously froma single strip rather than separately manufactured. Doing so avoids theneed to weld or clamp the components together, reducing the possibilityof stresses or non-uniformities forming during their joining. It alsodecreases the manual labor often involved in manufacturing existingdead-ends, permitting continuous automatic or semi-automatic manufactureto occur.

Using appropriate guides, such as rollers and wheels, the presentinvention manipulates a continuous flat strip or other suitable materialto form both helical and non-helical sections. Feeding the stripinitially to a pair of forming members, the invention permits devices ofdiffering pitch lengths and helix diameters to be formed, for example byadjusting the angle between feed and forming axes and the distancebetween the forming members. Such adjustments can occur automatically,moreover, by connecting the forming members to suitable controllers.Thus, although some embodiments of the present invention contemplateforming devices having sections of identical pitch length, the inventionis not so limited and may be used to produce devices of variable pitchlength and helix diameter. In particular, the present invention isuseful in forming insulator ties and other equipment typicallyassociated with conductive cables.

To make a dead-end consistent with the present invention, however, oneneed merely feed a flat strip of material to a pair of forming rollersor other forming members. After the first helical leg of the dead-end iscreated, the forming rollers may be deactivated to retain a straightsection of the device. During this operation other rollers may beemployed to bend, or redirect, the straight section along the same axisas that of the prior helical portion. Alternatively, the first helicalleg may simply be bent back to the original feed axis. In either event,maintaining the same axis of travel for both the helical and non-helicalsections of the device prevents it from effectively becoming a giantflywheel as it rotates during the forming process.

The forming rollers are thereafter reactivated to form the secondhelical leg of the device, and a cutting mechanism may be used toseparate adjacent devices. The straight section of the stripsubsequently is manually or automatically bent to form the bight of thecompleted dead-end. If a knurled surface is desired for the dead-end, itmay be formed in-line using a knurling wheel actuated hydraulically orotherwise.

The present invention has the virtue of providing devices formed ofcontinuous segments of the strip, avoiding the need to weld, clamp, orotherwise join their component parts. so leading to improved speed andcost of manufacture and to improved physical characteristics.

Other features. and advantages of the present invention will becomeapparent from the remainder of the description with reference to theclaims and drawings of the application.

FIG. 1 is a schematic representation of apparatus of the presentinvention with a knurling wheel activated.

FIG. 2 is a schematic representation of the apparatus of FIG. 1 with theknurling wheel deactivated.

FIG. 3 is a plan view of forming rollers of the apparatus of FIG. 1.

FIG. 3A is a cross-sectional view of the forming rollers taken alongline A--A of FIG. 3.

FIG. 4 is a plan view of redirection rollers of the apparatus of FIG. 1shown engaging a straight section of a device having both straight andhelical sections.

FIG. 5 is a plan view of forming rollers shown engaging a helicalsection of the device of FIG. 4.

FIG. 6 is a side elevational view of a dead-end of the presentinvention.

FIGS. 7 and 7A are respectively, top plan and side elevational views ofan insulator tie of the present invention.

FIG. 8 is a front elevational view of another insulator tie of thepresent invention.

FIGS. 1-2 illustrate schematically apparatus 10 in accordance with thepresent invention. Apparatus 10 includes drive section 14. comprisingone or more pairs of opposed drive wheels 18, and guides 22. The designof drive section 14 permits material 26, typically (but not necessarily)a flat strip of metal, to pass therethrough in the direction of feedarrow 30. Appropriate positioning of the drive wheels 18 and guides 22reduces the likelihood that material 26 will buckle or otherwise deformwhen fed to apparatus 10. Guides 22 also may be used to straightenmaterial 26 in one or more dimensions, thereby reducing warps and curvesthat might otherwise be present.

Because material 26 may be formed into articles usefull in connectionwith cable and wire installations knurling of at least portions of itssurface may be desired. As detailed in the schematic representations ofFIGS. 1-2. this knurling may be accomplished by including in apparatus10 a retractable knurl wheel 34. In FIG. 1. knurl wheel 34 is showncontacting material 26, producing thereon knurls suitable to enhance thegrip of material 26 about a cable or other object. In FIG. 2, bycontrast, knurl wheel 34 is retracted so as not to contact material 26.

As illustrated in FIGS. 1-2. knurl wheel 34 may be attached to hydrauliccylinder 38 to permit such retraction. Those skilled in the art willrecognized. however, that pneumatic cylinders or other actuators may beused to move knurl wheel 34 relative to material 26. Similarly. althoughknurl wheel 34 is shown schematically opposite drive wheel 18A andintermediate drive wheels 18 and guides 22. it may be positionedelsewhere as necessary or appropriate to achieve the sought afterresults.

Other apparatus may be installed to mark the strip surface, e.g. withpart numbers or trade marks by any known method--for example by lasermarking, printing, spraying, stamping or labelling.

Throughout drive section 14. material 26 (albeit possibly knurled orotherwise marked) remains flat. Upon exiting guides 22, however,material 26 encounters forming section 42, illustrated in FIGS. 3 and 3Aas including top forming roller 42A and bottom forming roller 42B havinglongitudinal axis C. Like knurling wheel 34. forming rollers 42A and 42Bare retractable and thus may be deactivated when desired. Alternatively.forming section 42 may comprise a single top forming roller 42A. withbottom forming roller 42B replaced by a support or, perhaps, thetrailing edge or portion of guides 22.

When activated, forming rollers 42A and 42B impart a helical shape untothe material 26 passing therethrough by bending and twisting thematerial 26. The distance D between forming rollers 42A and 42B maydetermine the diameter of helix 46 formed in material 26 so that,helixes of different diameters may be formed merely by adjusting thatdistance D. An alternative approach is to vary the angle F between aplane containing the rotational axes of the rollers 42A and 42B and thedirection of travel of material 26. This may be done in combination withadjusting distance D. Rollers 42A and 42B simultaneously change thedirection of travel of material 26 by an angle B. causing material 26 torange along longitudinal axis C rather than the original feed axis A.Thus, helixes 46 of different pitch lengths may be created by adjustingthe angle B between longitudinal axis C and feed axis A. By connectingforming rollers 42A and 42B to suitable controlling equipment, moreover,such adjustment of distance D and angle B may occur automatically.Moreover, by making angle B negative, helixes 46 having an opposite laydirection may be formed.

In essence as each part of the strip material is passed through therollers it is bent away from its initial direction of travel andtwisted. In the example shown in FIGS. 3 and 3A the bending is to anextent determined by the distance D and the twisting is to an extentdetermined by the angle B. It is this bending and twisting that producesthe helix.

The shapes of products such as dead-end 50 and insulator ties 54 and 58(see FIGS. 6, 7, 7A, and 8) are typically discontinuous. When producingthese products, therefore, after helix 46 is formed a non-helicalsection 62 must be created in material 26. This type of discontinuityillustrates some of the limitations of the techniques described in the'491 and '397 patents, which cannot produce such products from acontinuous strip.

By contrast. the present invention allows maintenance of a straightsection as non-helical section 62, created by deactivating formingrollers 42A and 42B and continuing to pass material 26 through formingsection 42. Although non-helical section 62 may be formed in thismanner, doing so would cause helix 46 of material 26 to act like aflywheel as it rotated. Accordingly, apparatus 10 of the presentinvention may also include redirection rollers 66A and 66B as shown inFIG. 4. Of differing diameters. opposed rollers 66A and 66B bend. orguide. non-helical section 62 along longitudinal axis C. Alternatively,helix 46 could simply be bent back to the original feed axis A.

Like forming rollers 42A and 42B. redirection rollers 66A and 66B areretractable, permitting them to be employed as necessary duringoperation of apparatus 10. Those skilled in the pertinent art willrecognize that servo motors, hydraulics, pneumatics, or any othersuitable mechanism may be used to retract and reactivate any or all offorming rollers 42A and 42B and redirection rollers 66A and 66B.Material 26 typically does not advance through apparatus 10 while suchretractions and reactivations occur, although with existing controllersthese actions can be performed almost instantaneously.

Deactivating rollers 66A and 66B and reactivating forming rollers 42Aand 42B produces another helix 70. Alternatively a single set of rollersmay be used for this purpose and moved from a forming position to aredirection position.

Although the present invention allows formation with greater uniformityof products having helixes 46 and 70 of the same diameter and pitchlength, such is not a necessary result of use of apparatus 10. Instead,as discussed above, adjusting the angle B and the distance D betweenforming rollers 42A and 42B permits helical devices of differing pitchlengths and helix diameters to be formed, with the adjustment occurringautomatically (even during formation of a single helix 46 or 70) ifdesired. The portion of material 26 to be used for a dead-end 50 or aninsulator tie 54 or 58 is cut after helix 70 is formed thereby producinga helical device having non-helical section 62 intermediate helixes 46and 70 and permitting continuous formation of the next such device.

FIG. 6 illustrates a dead-end 50 of the present invention. Dead-end 50is formed of a continuous strip of material 26 and comprises helix 46,helix 70, and non-helical section 62. Although generally straight whenexiting apparatus 10, non-helical section 62 of dead-end 50 has beencurved (either manually or using other equipment) to form bight 74 andso that leg 78 (comprising helix 46) is approximately parallel to leg 82(comprising helix 70). In the particular dead-end 50 shown in FIG. 6,the pitch length of helixes 46 and 70 is 2.85" (about 72.4 mm), whilethe outer diameter (the sum of the helix diameter and twice thethickness of the flat strip) of each of helixes 46 and 70 is 0.457"(about 11.6 mm). The strip may be, for example. 0.05" (about 1.3 mm) to0.5" (about 12.7 mm) thick and of a width 0.1" (about 2.5 mm) to 1"(about 25.4 mm) wide with the ratio of thickness to width between 2 and10.

FIGS. 7 and 7A detail an exemplary insulator "top" tie 54 in whichnon-helical section 62 has been bent into bight 74 in the shape of an"S." Nominal pitch lengths and outer diameters for such a tie may be5.50" (about 139.7 mm) and 1.004" (about 25.5 mm), respectively. FIG. 8finally, shows an insulator "side" tie 58 of the present invention. Ininsulator tie 58. non-helical section 62 has been bent throughapproximately 300 to form bight 74. This produces a nominal angle E ofapproximately 120 between legs 78 and 82. Exemplary pitch lengths andouter diameters for helixes 46 and 70 of tie 58 are, respectively, 4.00"(about 101.6 mm) and 0.683" (about 17.3 mm).

In use, legs 78 and 82 typically wrap around a conductor or other cableto grip it securely. If present, the knurled surfaces of legs 78 and 82may enhance the grip and thereby provide an even more effective product.As noted above, the helical products of the present invention may beformed of a continuous strip of material (whether flat, round, orotherwise) and are not limited to two-legged devices such as dead-endsand insulator ties. Instead, the invention contemplates production ofvirtually any elongated device intended to have one or morediscontinuities along its length.

What is claimed is:
 1. A method for forming helical sections in stripmaterial, the method comprising the steps of:a) feeding the stripmaterial in a first direction to contact a pair of forming members, thestrip material passing from one side of the pair of forming members,through and between the pair of forming members, to exit from the otherside of the forming members; and b) the forming members acting to bendthe strip therebetween by an amount of bending and twist the striptherebetween by an amount of twisting to form a helical section leavingthe forming members in a second direction disposed from the firstdirection by an angle, the amount of bending determining the diameter ofthe helix and the amount of twisting determining the helical angle ofthe helix.
 2. A method as claimed in claim 1 in which the amount oftwisting is determined by the angle between the first and seconddirections.
 3. A method as claimed in claim 1 in which the formingmembers comprise a pair of spaced rollers (42A, 42B) with rotationalaxes angularly disposed to the first direction to lie parallel with thesecond direction.
 4. A method as claimed in claim 1 in which the formingmembers may be selectively disabled so as to selectively produce anon-helical section from the strip material adjacent a helical section.5. A method as claimed in claim 3 in which the spacing between therollers is selectively variable to alter the amount of bending.
 6. Amethod as claimed in claim 3 in which an angle between a planecontaining the rotational axes of the rollers and the first direction isselectively variable to vary the amount of bending.
 7. A method asclaimed in claim 3 in which an angle of disposition of the rotationalaxes of the spaced rollers to the first direction, and thereby the anglebetween the first and second directions, is selectively variable to varythe amount of twisting.
 8. A method as claimed in claim 5 in which thespacing between the rollers is varied while forming a helix so that thediameter of said helix is varied.
 9. A method as claimed in claim 6 inwhich the angle between a plane containing the rotational axes of therollers and the first direction is varied while forming a helix so thatthe diameter of said helix is varied.
 10. A method as claimed in claim 7in which the angle of disposition of the rotational axes of the spacedrollers to the first direction, and thereby the angle between the firstand second directions, is varied while forming a helix so that the pitchof said helix is varied.
 11. Apparatus for forming helical sections instrip material, comprising:a) a pair of forming members; b) means forfeeding the strip material in a first direction to contact and passthrough and between the pair of forming members, the pair of formingmembers being operable to bend and twist the strip material therebetweento form a helical section leaving the forming in a second direction, theangle between the first and second directions determining the helicalangle of the helical section; c) the forming members being disposed tooperate such that in use the strip material passes from one side of thepair of forming members, through and between the pair of formingmembers, to exit from the other side of the pair of forming members. 12.Apparatus as claimed in claim 11 in which the forming members comprise apair of spaced rollers with rotational axes angularly disposed to thefirst direction to lie parallel with the second direction.
 13. Apparatusas claimed in claim 8 in which the forming members may be selectivelydisabled so as to selectively produce a non-helical section from thestrip material adjacent a helical section.
 14. Apparatus as claimed inclaim 12 in which the spacing between the rollers is selectivelyvariable to alter the amount of bending.
 15. Apparatus as claimed inclaim 9 in which an angle between a plane containing the rotational axesof the rollers and the first direction is selectively variable to varythe amount of bending.
 16. Apparatus as claimed in claim 9 in which anangle of disposition of the rotational axes of the spaced rollers to thefirst direction, and thereby the angle between the first and seconddirections, is selectively variable to vary the amount of twisting. 17.Apparatus as claimed in claim 14 in which the spacing between therollers is variable while forming a helix so that the diameter of saidhelix is variable.
 18. Apparatus as claimed in claim 15 in which theangle between a plane containing the rotational axes of the rollers andthe first direction is variable while forming a helix so that thediameter of said helix is variable.
 19. Apparatus as claimed in claim 16in which the angle of disposition of the rotational axes of the spacedrollers to the first direction, and thereby the angle between the firstand second directions, is variable while forming a helix so that thepitch of said helix is variable.
 20. A method of producing helicaldevices comprising a first helical section, a second non-helicalsection, and a third helical section, the method comprising the stepsof:a) feeding strip material having integrally formed first, second andthird sections to an apparatus; b) within the apparatus automaticallyactivating helix forming means to form the first section into the shapeof a helix; c) within the apparatus automatically inactivating the helixforming means so as not to form the second section into the shape of ahelix; d) within the apparatus automatically activating the helixforming means so as to form the third section into the shape of a helix;e) cutting the first section, second section, and third section from thestrip material to form a first helical device; and f) repeating stepsa)-e) to form a second helical device the cutting of the preceding stepe) severing the third section of the first helical device from the firstsection of the second helical device.
 21. A method as claimed in claim20 which includes the step of bending the second section into a curve.22. A method as claimed in claim 14 including the step of knurling thestrip material.
 23. A method as claimed in claim 20 in which thehelix-forming means is selectively varied while forming a helicalsection so that the diameter of said helical section is varied.
 24. Amethod as claimed in claim 20 in which the helix-forming means isselectively varied while forming a helical section so that the pitch ofsaid helical section is varied.
 25. A method of producing helicaldevices comprising a first helical section, a second non-helicalsection, and a third helical section, the method comprising the stepsof:a) feeding strip material having integrally formed first, second, andthird sections to an apparatus; b) within the apparatus automaticallyoperating helix-forming means to form the first section into the shapeof a helix; c) within the apparatus automatically deactivating thehelix-forming means so as not to form the second section into the shapeof a helix; d) within the apparatus automatically activating thehelix-forming means so as to form the third section into the shape of ahelix and thereby form a first helical device; e) repeating steps a)-d)to form a second helical device connected to the first helical device;and f) using a cutting mechanism to disconnect the first and secondhelical devices.
 26. A method according to claim 25 in which thehelix-forming means is selectively varied while forming a helicalsection so that the diameter of said helical section is varied.
 27. Amethod as claimed in claim 25 in which the helix-forming means isselectively varied while forming a helical section so that the pitch ofsaid helical section is varied.
 28. A method as claimed in claim 25further comprising the step of bending the second section into a curve.29. A method as claimed in claim 25 further comprising the step ofknurling the strip material.